Field of the Disclosure
The present disclosure generally relates to the processing of heavy reformate. More specifically, embodiments of the disclosure relate to the production of para-xylene and benzene from heavy reformate.
Description of the Related Art
Petrochemical refiners are facing issues with utilization of heavy reformate streams. Environmental regulations by governments and regions around the world are limiting the amount of aromatics (C6+) content in gasoline fuel. Gasoline refiners and blenders traditionally use C6+ aromatics, which include the C6-8 BTEX components (benzene, toluene, ethylbenzene, and xylenes), to improve octane ratings and anti-knocking attributes of motor fuels
Although motor fuel use is a major consumer of BTEX components, each of the BTEX products has alternative markets for their use besides motor fuels. Benzene is a widely used precursor for many chemical and solvation processes. Toluene and ethylbenzene are also reactants and precursors in chemical and polymerization processes. The three isomers of xylene (C8H10)—para-xylene (p-xylene), meta-xylene (m-xylene), and ortho-xylene (o-xylene)—are all petrochemical feedstocks of value. When mixed xylenes form during catalytic reformation, the less commercially valuable m-xylene forms in greater amounts than either p- or o-xylenes because of thermodynamic equilibrium relationships between the three isomers. Market demand, however, currently favors p-xylene followed distantly by o-xylene.
Reformate, the bottoms product from naphtha catalytic reforming, and pyrolysis gasoline (“pygas”), a byproduct of ethylene cracking, are the usual sources for these compounds. Extracting the valuable BTEX components from reformate and pygas leaves a heavy reformate, which includes mainly C9+ alkyl aromatic compounds (pygas may also contain diolefins if not previously separated). Heavy reformate can also form from running these processes at higher severity (that is, temperatures) to produce more hydrogen, alkanes and olefins from naphtha.